Vertical Cavity Surface Emitting Laser (VCSEL) devices are used in some printers. VCSEL devices may be turned on and off by providing a drive current pulse at a current value above the threshold necessary to stimulate emission of light. The emitted light pulses are directed onto areas to be printed.
VCSEL devices have a laser light power output characteristic in which the output power changes over time when turned on and the output power at the beginning of an “on” pulse is different from the output power at the end of a previous “on” pulse.
A printer may have image processing or a print engine which determines when a VCSEL laser should be on to expose a particular pixel or sub-pixel. The image processing or print engine may be programmed to determine the proper exposure based on a nominal output power. However, given the variations in time during when a VCSEL is on and between successive pulses, the actual exposure for a given pixel or sub-pixel may be less than or more than the expected or nominal pixel which the image processing and/or print engine intended to produce which may introduce imperfections in the printed image.